The lipid structure and metabolism of cultured minimal deviation hepatoma cells, hepatoma grown in host, host liver, and normal rat liver are being studied. All lipid classes are being studied. All lipid classes are being examined in whole cells, organelles, and membrane fractions. Hepatoma cells cultured on varying amounts of serum and lipid showed only marginal changes in lipid class composition, whereas the monoenoic fatty acid concentrations increased as the quantity of media lipids was decreased. Media lipid levels never decreased and in most cases increased indicating that these hepatoma cells excrete some lipids. The cultured hepatoma cells or media did not contain detectable levels of glyceryl ether diesters, a lipid thought to be characteristic of tumors. The use or radioactive lipids and precursors indicate that these cultured hepatoma cells can synthesize most if not all of their complex lipids. Host grown minimal deviation hepatoma contained higher levels of free sterols, sterol esters, and sphingomyelin and decreased concentrations of phosphatidylcholine relative to either host liver or normal liver. Generally, the neutral lipids of the solid hepatoma contained much higher levels of polyunsaturated fatty acids than host or normal liver whereas hepatoma phospholipid contained decreased concentrations of polyenoic acids relative to host or normal rat liver. The studies carried out thus far have shown that the lipid metabolism in this minimal deviation hepatoma differ from that of host or normal liver. Work is continuing to explain the observed differences.